For the cake layers
250 grams soft flour
50 grams cornflour (corn starch)
20 grams unsweetened cocoa powder
2 teaspoons baking powder
1 teaspoon baking soda
150 grams sugar
2 eggs
2 tablespoons Nutella
250 grams plain yoghurt
120 ml oil
2 teaspoons vanilla
For the filling
200 ml double cream
200 grams milk chocolate
100 grams Nutella
Preparation
Sift together the flour, cornflour (corn starch), cocoa powder, baking powder and baking soda at least twice, and set it aside. Beat the eggs with an electric mixer on high for 2 minutes, add the sugar and beat for another 5 minutes on high, until the batter becomes lighter in colour and thick. Add Nutella and blend well. Whisk together the yoghurt, oil and vanilla in another bowl. Pour one third in the egg batter, along with a third of the flour mixture and beat on low until combined. Repeat this two more times, until you use up all of the ingredients, then quickly pour the batter into two prepared baking pans (23cm/9-inch, lined with baking paper) and bake in a preheated oven, at 180˚C (350˚F) for 15-20 minutes. Check them with a toothpick, to make sure they don't overbake. Leave them in the pans for a few minutes, then transfer to cooling racks and let them cool down completely.
For the filling, chop up the milk chocolate, put it in a large bowl, add room temperature Nutella and set it aside. Heat up the double cream over medium heat and bring it almost to a boil (do not let it come to a boil), remove from heat and quickly pour it over the chocolate and Nutella. Let it stand for a minute or two, then mix with a wooden spoon or a spatula, until everything is well blended and smooth. Let the filling sit at room temperature until it cools down and thickens up enough to be spread on the cake.
While the filling is cooling, level the cakes if they rose unevenly. When the filling is ready, put one of the cakes on a serving platter, put a spring-form ring around it and close it, then spread evenly the filling. Put the other cake in the ring, cover the entire thing with plastic wrap and let it sit in the fridge for at least 8 hours. Decorate to your liking and serve.
